In the examination of tyres, by means of X-ray radiation, for production faults, an X-ray line detector is used which has the shape of a horseshoe, thus is U-shaped in top view. Aligned inwardly along the course of the horseshoe there is an inlet slot which extends over the entire horseshoe and behind which photodiodes detect a fan-shaped X-ray beam, after the latter has passed through the tyre and been converted by a scintillator. The exact positioning of the photodiodes behind the inlet slot is an operation that, in situ, is mechanically very elaborate and time-intensive, wherein an iterative procedure is normally required for the fine adjustment. The photodiodes located on a printed circuit board—of which a plurality are arranged next to each other—have a multiplicity of individual pixels. The individual pixels are in each case connected to a multiplexer via an electrical line. From the multiplexer, the data originating from the individual pixels are forwarded, via a data line, to an A/D converter, located outside of the X-ray line detector on a separate printed circuit board. In this case, usually only one single A/D converter is used for the data from many or all photodiodes. The then digitized data are processed, by means of methods known to a person skilled in the art, and finally converted into an image of the screened tyre, which can be viewed on the monitor screen by an operator. On the basis of this image, the operator then decides whether the tyre is defective.
On the one hand, such an X-ray line detector is mechanically complex in its structure, since many components are needed in order to achieve the fine adjustment of the individual photodiodes in relation to each other so as to obtain an image that has informative value for the operator. Moreover, such an X-ray line detector is also disadvantageous in respect of the electronics, since the image quality is not particularly good, owing to interfering signals and distortions.